我已经运行了Visual Studio的性能诊断程序,并发现一个单独的函数在66%的时间运行,即以下类的GetHashCode函数.
Public Class Identifier Public Property Name As String Public Overrides Function GetHashCode() As Integer Return Name.toupper().GetHashCode() End Function Public Overrides Function Equals(other As Object) As Boolean Dim otherIdentifier = TryCast(other,Identifier) If otherIdentifier Is nothing Then Return False Else Return String.Equals(Name,otherIdentifier.Name,StringComparison.InvariantCultureIgnoreCase) End If End Function End Class
让我更加困惑的是,在“被调用的功能”面板中,我读到了,在经历的包容时间方面:
> System.String.toupper():0.61%
> System.String.GetHashCode():0.21%
>功能体:66.67%
由于函数除了调用toupper和GetHashCode函数之外什么都不做,我很难搞清楚我在这里可以改进什么.
你能帮我解释一下吗?
Function Body
also shows you the total amount of time (and the
percentage of time) spent in the function body excluding time spent in
calling and called functions
但它并没有真正解释为什么在排除对toupper和GetHashCode的调用时,在GetHashCode中花费了2/3的时间.
然而..
“High values in Function Body may indicate a performance bottleneck
within the function itself”
很明显,toupper总是必须为它必须比较的每个字符串创建一个新字符串.如果你这样做了数百万次,你就会有很高的内存压力并且GC会启动.这就是为什么我会使用StringComparer:
Public Overrides Function GetHashCode() As Integer Return StringComparer.InvariantCultureIgnoreCase.GetHashCode(Name) End Function
您也可以在Equals中使用它
Public Overrides Function Equals(other As Object) As Boolean Dim otherIdentifier = TryCast(other,Identifier) If otherIdentifier Is nothing Then Return False Return StringComparer.InvariantCultureIgnoreCase.Equals(Name,otherIdentifier.Name) End Function
原文地址:https://www.jb51.cc/vb/255301.html
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